The present invention relates to a container for delivering fluids. In particular, it relates to a peelable seal between chambers of a multiple chambered container to separately store two or more components for administering to a patient. The components can be in a powder or liquid form and are typically mixed together to form a therapeutic solution. Such solutions can include intravenous solutions, nutritional solutions, drug solutions, enteral solutions, parenteral solutions, dialysis solutions, pharmacological agents including gene therapy and chemotherapy agents, and many other fluids that may be administered to a patient.
Due to stability, compatibility, or other concerns, some medical solutions have to be stored separately prior to administration to a patient. These solutions may be stored in separate containers, but are often stored in separate chambers of a single container. The chambers and solutions are often separated by a frangible heat seal. Examples of such containers are disclosed in U.S. Pat. Nos. 5,209,347; 5,176,634; and 4,608,043. These prior art containers have frangible seals to permit the seal to be broken by hand pressure against the sides of the bag to force the contents to break the seal and permit mixing between the components. Peelable seals are among the frangible seals used that permit the seal to be separated by pulling on opposite sides of the container, or by squeezing the container sidewalls.
The chambered container is typically made of flexible polymeric materials. Numerous polymeric films have been developed for use in such containers, and can be a monolayer structure or a multiple layer structure. The monolayer structure can be made from a single polymer, or from a polymer blend. Multiple layer structures can be formed by co-extrusion, extrusion lamination, lamination, or any suitable means. The multiple layer structures can include layers such as a solution contact layer, a scratch resistant layer, a barrier layer for preventing permeation of oxygen or water vapor, tie layers, or other layers. Selection of the appropriate film depends on the solution to be contained within the container.
The container is typically formed by placing one or more polymeric film sheets in registration by their peripheral portions and sealing the outer periphery to form a fluid tight pouch. The peripheral seals are permanent, and therefore, do not peel. The sheets are sealed by heat sealing, radio frequency sealing, thermal transfer welding, adhesive sealing, solvent bonding, and ultrasonic or laser welding.
Blown extrusion is another method used to make the pouch. Blown extrusion is a process that provides a moving tube of extrudate exiting an extrusion die. Air under pressure inflates the tube. Longitudinal ends of the tube are sealed to form the pouch. A blown extrusion process only requires forming seals along two peripheral surfaces, where the single or multiple sheet registration method requires seals along one, three, or four peripheral surfaces to form the pouch.
A peelable seal having a peel strength lower than the peripheral seal can be formed in the container by various methods such as using a lower heat sealing temperature than used to form the peripheral seal. A peelable seal typically has an initial or peak peel force required to initiate separation of the peelable seal, and a plateau force to propagate the separation. Before steam sterilization, these forces are essentially equal. After the chambered container is filled with solution, it is typically steam sterilized at a temperature of 121° C. During steam sterilization, stress is applied to the edges of the peelable seal. When stress is applied to the peelable seal at a temperature above the softening point of the container material during sterilization, deformation occurs at the seal edge. The deformation reduces stress concentrations at the edge of the seal, increasing the peak peel force necessary to initiate peeling of the peelable seal. After steam sterilization, the peak peel force can be significantly greater than the plateau force. This increased peak peel force is detrimental to use of the multichambered container by making it more difficult to initiate peeling to open the container. This is especially true for patients using the medical solutions who may be infirmed or elderly and unable to provide the force necessary to initiate peeling. Moreover, the peak peel force is difficult to control, some containers remaining easy to initiate peeling in the peelable seal, while others becoming almost impossible to initiate by hand.